The present invention generally relates to apparatus for separation of solids suspended in a liquid and, more particularly, to an improved lamella-type gravity separator.
Settling tanks and clarifiers have been used for many years to separate solids suspended in water and wastewater. Such approaches include simple concrete or steel tanks where water containing suspended solids flowed in, was retained for a predetermined length of time, and departed, substantially free of suspended solids. Various advancements were made over the years to increase the efficiency of such apparatus; including the incorporation of sludge removal mechanisms, flocculators and sludge recycle mechanisms. Settling tanks, however, are often directed to biological waste and non-abrasive materials having a comparatively small particle size, and thus may be too expensive and insufficiently robust in handling a broad array of operating conditions and particle sizes. Moreover, such systems are often incapable of handling non-ambient fluid streams, such as coal combustion residue water streams.
In recent years, the separation art has included applications of lamella separation. Lamella separation separates solids from a carrying liquid by directing the liquid between series of inclined plates (lamellae). The effective settling area of each lamella plate is equivalent to the horizontal projection of that lamella plate. Lamella plates are typically spaced a few inches apart, with the result that large settling surfaces are concentrated within a relatively small area. The lamella separation promotes laminar flow conditions systems where they are used, which leads to a very high degree of separation. However, such applications are typically impractical for variable flow applications where an adjustment in volume or weir height may be needed. Furthermore, some lamella plate applications may require a high number of lamella plates which may be impractical from the viewpoint of cost and/or operation.
Thus, the present state of the art reflects a need for a system which reliably and efficiently processes coal combustion residue in a continuous dewatering recirculation system while reducing or eliminating any reliance upon a clarifier or other expensive equipment.